CITRICUI/TURE 


Webber,  Herbert  J. 


THE  EFFECT  OF  RESEARCH  IN 

GENETICS  ON  THE  ART 

OF  BREEDING 


PATER  No.  27,  DEPARTMENT  OF  PLANT-BREEDING 
CORNELL  UNIVERSITY,  ITHACA,  N.  Y. 


Reprint  from  Science,  N.  S.,  Vol.  35,  No. 
p.  597-CO'J,  April  19,  1912. 


[Reprinted  from  SCIENCE,  N.  S.,  Vol.  XXXV.,  No.  90S,  Page  597-609,  April  19,  1912] 


THE  EFFECT  OF  RESEARCH  IN  GENETICS  ON  THE  ART  OF 

BREEDING* 


o 


THE  knowledge  of  breeding  has  advanced 
so  rapidly  in  recent  years  that  few  of  us 
realize  the  great  change  that  has  taken 
place  in  our  understanding  of  the  funda- 
mental principles,  and  the  effect  that  this 
change  has  had  on  the  methods  of  practical 
breeding  which  we  advocate.  I  had  the 
good  fortune  to  begin  my  studies  and  ex- 
periments in  breeding  in  1890,  ten  years 
before  the  rediscovery  of  Mendel's  now 
famous  principles  of  heredity,  or  the  pub- 
lication of  de  Vries's  mutation  theory. 
I  have  thus  had  the  opportunity  to  follow 
this  change  through  all  its  ramifications. 
From  a  condition  of  ignorance  and  largely 
of  chaos,  where  all  advance  was  taken  as  a 
lucky  chance,  we  have  developed  to  a  posi- 
tion where  practically  each  step  may  be 
taken  intelligently.  True,  we  touch  the 
limits  of  knowledge  on  every  hand  and 
many  of  the  most  fundamental  problems 
still  remain  unsolved,  yet  our  understand- 
ing to-day,  which  enables  us  to  analyze  a 
plant  into  its  component  parts  or  charac- 
ters, and  then  in  turn  by  synthesis  to  build 
up  a  new  structure  by  the  combination  of 
different  characters  into  a  new  race  or 
variety,  is  to  our  former  understanding 
as  light  to  darkness.  The  knowledge  of 
breeding  has  developed  into  the  science  of 

1  Paper  No.  27,  Department  of  Plant  Breeding, 
Cornell  University,  Ithaca,  New  York.  Annual 
address  of  retiring  chairman  of  the  Plant  Section, 
American  Breeders'  Association. 


genetics,  and  is  fast  assuming  through 
the  orderly  presentation  and  classification 
of  facts,  the  form  of  an  exact  science.  Yet 
with  all  this  advance  in  our  understanding, 
the  methods  of  breeding  that  can  be 
recommended  for  the  use  of  practical 
breeders  have  changed  but  little  in  the  last 
twenty  years,  the  greatest  change  being 
primarily  in  the  greater  surety  with  which 
we  now  make  recommendations.  It  is  the 
speaker's  purpose  in  this  address  to  em- 
phasize certain  salient  features  of  the  ad- 
vance that  has  been  achieved,  and  point 
out  what  he  conceives  to  be  some  of  the 
most  important  problems  awaiting  solution. 

Twenty  years  ago  our  understanding  of 
the  principles  of  breeding  was  derived 
largely  from  Knight's  physiological  papers 
and  Darwin's  "Origin  of  Species"  and 
"Plants  and  Animals  under  Domestica- 
tion." Verlot's  admirable  pamphlet  "On 
the  Production  and  Fixation  of  Varieties 
of  Ornamental  Plants ' '  gave  a  general  out- 
line of  the  best  methods  then  followed,  and 
we  derived  our  knowledge  of  the  use  of 
hybrids  largely  from  Focke  's  excellent  text, 
"Die  Pflanzenmischlinge,"  published  in 
1880,  and  the  work  of  the  French  experi- 
menter Naudin. 

At  that  time  breeders  clearly  understood 
the  fact  that  hybrids  segregated  in  the  sec- 
ond generation  and  gave  new  combinations 
of  characters,  and  the  suggestion  was  even 
then  present  in  the  minds  of  scientific 


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SCIENCE 


breeders,  that  this  segregation  of  characters 
took  place  during  the  reduction  division. 
At  that  time  breeders,  just  as  definitely  as 
now,  planned  experiments  in  hybridizing 
different  varieties  or  species  to  secure  cer- 
tain recombinations  of  desired  characters 
in  the  hybrids.  The  experiments  in  citrus 
hybridization  conducted  by  Mr.  W.  T. 
Swingle  and  the  speaker  were  planned  in 
1893  entirely  on  this  basis,  yet  the  prin- 
ciple was  in  no  sense  of  the  word  original 
with  us,  but  was  at  that  time  well  under- 
stood by  all  practical  breeders.  This 
understanding,  the  speaker  thinks,  was 
largely  derived  from  the  investigations  of 
Naudin,  though  various  investigators  con- 
tributed to  it. 

With  a  full  understanding  of  the  knowl- 
edge and  practises  of  the  breeders  of  two 
decades  ago,  it  must  be  admitted  that  the 
conception  of  unit  characters  and  Men- 
delian  segregation  was  necessary  to  clarify 
this  knowledge  and  bring  out  the  latent 
possibilities  of  the  material  presented  by 
nature  for  the  use  of  the  breeder,  and  it  is 
doubtful  whether  we  even  yet  adequately 
comprehend  the  almost  infinite  possibilities 
open  to  us. 

To  understand  breeding  to-day  we  must 
clearly  understand  the  conception  of  unit 
characters.  We  no  longer  conceive  the 
species,  race  or  variety,  as  a  fixed  ensemble 
of  characters.  Following  De  Vries,  we  now 
commonly  conceive  the  species  or  variety 
to  be  made  up  of  a  certain  number  of  unit 
characters,  that  are  in  large  measure  as- 
sociated together  by  the  accident  of  evolu- 
tion or  breeding  and  which  are  separable 
entities  in  inheritance.  We  may  liken 
these  unit  characters  to  bricks  used  in  the 
construction  of  a  building,  each  separate 
and  yet  dependent  on  the  others  for  the 
maintenance  of  the  structure ;  as  each  unit 
character  is  dependent  on  the  other  unit 
characters  for  the  maintenance  of  the 


plant  body.  We  may  think  of  these  unit 
characters  as  organic  elements  similar  to 
chemical  elements,  that  by  their  recom- 
bination through  hybridization,  form  new 
compounds — new  plants — of  distinctly  dif- 
ferent appearance,  but  which  in  turn  do 
not  affect  the  unit  characters,  which  may 
again  be  separated  and  led  to  form  other 
compounds,  again  resulting  in  distinct  or- 
ganisms. Related  species  may  possess 
many  distinct  unit  characters,  but  ordi- 
narily would  be  expected  to  possess  many 
similar  unit  characters.  Cultivated  races 
or  varieties  ordinarily  would  differ  only  in 
a  few  unit  characters,  and  difference  in  a 
single  unit  character  would  be  sufficient  to 
give  a  distinct  and  recognizable  race  or 
variety.  Indeed,  the  difference  between 
two  varieties  of  a  single  unit  character 
might  mean  that  one  variety  would  be 
exceedingly  valuable  and  the  other  prac- 
tically worthless.  De  Vries  asserts  that 
unit  characters  are  discontinuous  in  inherit- 
ance and  do  not  exhibit  transitional  forms. 
A  plant  can  not  be  hairy  and  at  the  same 
time  smooth,  or  a  fruit  yellow  and  at  the 
same  time  red.  While  there  is  yet  much 
difference  of  opinion  on  these  questions  the 
preponderance  of  evidence  certainly  favors 
the  unit  character  conception. 

If,  then,  we  recognize  that  species  are 
made  up  of  unit  characters  and  that  dif- 
ferent species  differ  in  the  possession  of 
different  unit  characters,  the  great  problem 
in  the  evolution  of  species  becomes  the 
question  of  how  the  new  unit  character  is 
acquired.  Have  all  unit  characters  existed 
from  the  beginning,  or  are  new  unit  char- 
acters being  continuously  acquired?  A 
few  years  ago  we  supposed  that  new  char- 
acters, if  acquired  in  any  form,  must  be 
seized  upon,  as  it  were,  by  natural  selec- 
tion and  preserved,  or  otherwise  that  they 
would  be  swamped  by  intercrossing  and  lost. 
We  now  know  from  Mendelian  analysis  that 


SCIENCE 


a  unit  character  may  be  apparently  lost  in 
crossing,  owing  to  the  prevailing  presence 
of  its  dominant  allelomorph,  but  that  in 
reality  it  is  not  lost  or  apparently  changed 
and  will  reappear  again  when  it  happens 
that  two  gametes  both  bearing  the  character 
meet  in  fecundation.  It  may  remain  hid- 
den for  many  years,  but  as  we  are  now 
inclined  to  view  the  matter,  the  character 
or  the  determiner  of  the  character  would  not 
be  permanently  lost  to  the  species  unless  all 
individuals  possessing  it  were  killed  before 
they  produced  seed.  This  unit  character 
idea  would  lead  us  to  the  conception  of  the 
species  as  made  up  of  all  the  unit  char- 
acters that  it  has  acquired  by  any  means 
in  its  development  and  which  still  exist. 
The  acquirement  of  any  new  unit  character 
would  add  one  more  character  to  the  spe- 
cies and  double  the  number  of  possible 
varieties  or  races  of  the  species. 

In  evolutionary  studies  we  have  long 
recognized  that  variation  was  the  founda- 
tion of  evolution  and  that  no  evolution  was 
possible  without  variation,  but  we  have 
assigned  to  selection  an  all-important  part 
as  guiding  and  even  stimulating  the  varia- 
tion in  a  certain  direction.  Darwin  and 
particularly  some  of  his  more  radical  fol- 
lowers have  assigned  to  selection  a  creative 
force,  in  that  it  has  been  assumed  that  when 
nature  by  a  slight  variation  gave  the  hint 
of  a  possible  change  in  a  certain  direction, 
natural  or  artificial  selection,  by  choosing 
this  variant  and  selecting  from  among  its 
progeny  the  most  markedly  similar  vari- 
ants, could  force  the  advance  of  the  varia- 
tion in  the  direction  indicated.  Since 
Darwin's  time  this  cumulative  action  of 
selection  has  been  emphasized  so  forcibly 
that  we  had  come  to  recognize  selection  as 
an  active  force  in  creation  rather  than 
simply  as  a  selective  agency.  To  be  the 
vital  principle  of  evolution,  as  we  now 
understand  the  species  as  made  up  of  herit- 


able unit  characters,  the  selectionist  must 
show  that  a  new  character  can  be  created 
by  selection,  otherwise  selection  becomes  a 
secondary  principle. 

When  viewed  from  the  standpoint  of  the 
production  of  a  new  and  definitely  herit- 
able unit  which  mendelizes,  the  task  of 
selection  becomes  more  doubtful.  Dar- 
win's idea,  that  changes  in  species  required 
many  years  and  probably  many  centuries 
for  accomplishment,  took  the  subject 
largely  out  of  the  field  of  experimentation 
and  in  a  measure  developed  a  speculative 
science.  One  of  the  greatest  contributions 
to  science  made  by  De  Vries  was  to  estab- 
lish the  study  of  evolution  on  an  experi- 
mental basis.  With  the  demonstration  that 
evolution  could  be  studied  experimentally, 
the  question  of  the  effectiveness  of  selection 
was  taken  up,  and  we  are  now  doubtless  on  i 
the  road  to  a  solution  of  the  problem.  rf  It 
is  only  possible  for  us  here  to  call*  attention 
to  a  few  of  the  researches  in  this  direction. 

The  classical  researches  of  De  Vries,  now 
familiar  to  us  all,  challenged  the  correct- 
ness of  the  selection  theory  and  sought  to 
show  that  species  originated  by  sudden 
jumps  or  mutations.  We  may  admit  that 
De  Vries  proved  that  species  or  new  char- 
acters were  formed  suddenly  as  mutations, 
but  this  would  not  prove  that  they  might 
not  also  be  formed  or  actually  induced  to  mu- 
tate by  a  continuous  process  of  selection. 
Indeed,  in  his  experiments  on  the  produc- 
tion of  a  double-flowered  variety  of  Chrys- 
anthemum segetum  ("Mutationstheorie," 
Vol.  I.,  p.  523),  a  few  generations  of  selec- 
tion led  to  markedly  increasing  the  number 
of  ray-florets  before  the  ligulate  corollas 
appeared  among  the  disk-florets,  the  change 
which  he  interpreted  as  the  mutation  that 
gave  him  the  double  variety. 

Johannsen  has  contributed  much  to  our 
knowledge  of  selection  and  has  given  us  a 
more  exact  method  of  experimentation  by 


SCIENCE 


his  conception  of  pure  lines,  biotypes,  geno- 
types and  phenotypes.  His  experiments  in 
the  selection  of  pure  lines  of  beans  in  an 
attempt  to  produce  large  and  small  seeded 
types,  have  led  him  to  conclude  that  selec- 
tion within  a  pure  line  is  ineffective  in  pro- 
ducing changes.  He  did,  however,  secure 
new  types  from  pure  lines  through  muta- 
tions. 

Tower's  experiments  with  the  potato 
beetle  in  attempting  to  create  by  selection, 
large  and  small  races,  albinic  and  melanic 
races,  and  races  with  changed  color-pat- 
tern, although  conducted  carefully  for 
from  ten  to  twelve  generations,  failed  to 
give  any  evidence  of  producing  perma- 
nently changed  types.  While  strains  of 
plus  and  minus  variates  gave  populations 
with  a  range  of  variation  apparently  mark- 
edly restricted  to  their  respective  sides  of 
the  normal  variation  range,  still  these  se- 
lected strains  did  not  greatly  exceed  the 
normal  range  of  variation  in  either  direc- 
tion, and  when  the  selection  was  discon- 
tinued, in  two  or  three  generations,  again 
produced  populations  exhibiting  the  nor- 
mal range  of  variation.  Clearly  no  new 
unit  characters  had  been  added  by  the 
selection.  Tower,  however,  found  that  by 
subjecting  the  beetles,  during  the  process 
of  the  formation  of  gametes,  to  certain  ab- 
normal conditions,  he  was  likely  to  obtain 
mutations  in  the  progeny  that  would  imme- 
diately form  the  beginnings  of  new  races. 

Jennings  in  a  series  of  selection  experi- 
ments conducted  with  paramecium,  which 
were  continued  for  over  twenty  genera- 
tions, obtained  no  evidence  of  a  permanent 
modification  of  the  type. 

Pearl  has  conducted  an  extended  experi- 
ment in  the  selection  of  chickens  in  the 
attempt  to  produce  a  breed  of  high  egg- 
laying  capacity.  His  results  have  led  him 
to  the  conclusion  that  selection  alone  has  no 


effect  in  producing  a  permanent  improve- 
ment or  a  change  of  type. 

Up  to  the  present  time  these  are  the 
principal  contributions  to  the  subject, 
that  discredit  the  effectiveness  of  selec- 
tion as  an  active  agency. 

On  the  opposite  side  of  the  controversy 
we  have  the  very  careful  and  extensive  re- 
searches of  Castle  and  MacCurdy  in  the 
selection  of  Irish  rats  to  increase  the  black- 
colored  dorsal  band  on  the  one  hand  and  to 
decrease  or  obliterate  it  on  the  other. 
Castle  appears  to  have  obtained  very  posi- 
tive results  favoring  the  gradual  cumulative 
action  of  the  selection,  as  he  succeeded  in 
markedly  increasing  the  amount  of  black 
in  one  strain  until  the  rats  were  almost 
wholly  black,  and  in  the  other  strain  al- 
most wholly  obliterating  the  black.  The 
speaker  is  not  informed  whether  the  in- 
heritance in  hybridization  of  these  appar- 
ently new  characters  has  been  tested.  If 
a  new  character  has  been  added  it  should 
maintain  itself  and  segregate  after  hy- 
bridization. 

The  experiments  conducted  by  Dr. 
Smith  and  others  at  the  Illinois  Experi- 
ment Station  on  selecting  high  and  low 
strains  of  corn  with  reference  to  oil  and 
protein  content,  have  resulted  in  markedly 
distinct  strains  possessing  these  qualities, 
which  are  inherited  apparently  as  long  as 
the  selection  is  continued.  It  seems  certain 
that  the  oil  and  protein  content  has  been 
increased  considerably  beyond  the  maxi- 
mum which  existed  in  the  original  race. 
The  writer  is  informed  by  Dr.  Smith  that 
experiments  have  been  made  in  cultivating 
these  varieties  without  selection  and  that 
the  new  characters  have  been  maintained 
for  several  years  without  marked  regres- 
sion. We  must  apparently  conclude  then 
that  new  heritable  characters  have  been 
acquired  in  the  course  of  the  selection,  but 
it  will  probably  be  difficult  to  determine 


SCIENCE 


5 


whether  the  advance  is  to  be  considered  as 
a  cumulative  effect  of  the  selection  of  fluc- 
tuations or  the  gradual  purification  by  the 
selection,  of  mutants  which  occurred  during 
the  selection  or  possibly  even  before  the 
first  selections  were  made.  The  purifica- 
tion of  a  type  even  when  the  character  con- 
cerned is  easily  observable  is  known  to 
require  a  number  of  years  unless  both 
parents  are  carefully  followed.  Whether 
these  qualities  will  segregate  as  unit  char- 
acters after  hybridization  has  not  been 
determined  so  far  as  the  writer  is  informed. 

Very  many  cases  of  increases  obtained  in 
quantitative  characters  could  be  cited,  but 
the  majority  of  the  experiments  were  un- 
dertaken primarily  to  obtain  practical 
results,  and  whether  such  apparently  new 
characters  would  stand  the  test  of  unit 
characters  is  doubtful. 

The  improvement  of  the  sugar  beet  by 
selection  forms  a  typical  and  instructive 
case  of  this  kind.  The  careful  selection  of 
the  sugar  beet  was  started  over  sixty  years 
ago  by  Louis  Vilmorin,  at  which  time  a 
range  of  variation  in  sugar  content  of  from 
5  per  cent,  to  21  per  cent,  was  known  to 
exist.  Since  that  time  the  industry  has 
grown  extensively  until  hundreds  of  thou- 
sands of  beets  are  examined  annually  and 
the  richest  in  sugar  content  selected  for 
seed  production.  The  process  of  selecting 
the  beets  richest  in  sugar  content  for 
mothers  has  now  been  continued  for  sixty 
years  and  is  practised  extensively  every 
year,  and  yet  there  is  no  evidence  that  the 
maximum  sugar  content  has  been  increased, 
and  it  is  certain  that  the  character  of  rich- 
ness in  sugar  content  has  not  been  rendered 
permanently  heritable,  as  sugar  beet  grow- 
ers well  know  that  their  success  depends 
upon  the  continuance  of  the  selection. 
Here  it  is  certain  that  no  distinct  unit  char- 
acter has  been  added  by  the  continuous 
selection. 


The  strongest  evidence  as  to  the  method 
of  origin  of  new  characters  is  derived  nat- 
urally from  our  knowledge  of  known  cases 
of  the  origin  of  such  typical  new  charac- 
ters. When  we  view  the  evidence  critic- 
ally, I  think  it  must  be  admitted  that  in 
practically  all,  if  not  all,  of  the  cases  of 
new  characters  appearing,  they  have  come 
into  existence  suddenly.  The  cut-leaved 
Celedonium,  the  cupid  sweet  pea,  Bursa 
heegeri,  the  Otter  sheep,  the  muley  cow, 
are  illustrations  familiar  to  all  and  doubt- 
less each  of  us  could  add  several  such  illus- 
trations from  our  own  knowledge.  Such 
new  characters  appearing  suddenly  are 
heritable  and  maintain  themselves  as  unit 
characters  in  hybridization.  We  can  not 
but  admit  that  the  evidence  of  these  known 
cases  counts  against  the  origin  of  charac- 
ters by  gradual  cumulative  selection. 

In  summarizing  this  part  of  our  discus- 
sion, we  can  only  state  that  at  present  it 
appears  that  far  the  greatest  weight  of 
evidence  is  opposed  to  the  origin  of  a  new 
unit  character  through  the  cumulative  ac- 
tion of  selection. 

Are  we,  then,  to  conclude  that  the  prac- 
tise of  breeders  in  continually  selecting 
from  the  best  for  propagation  is  useless, 
and  must  we  advise  practical  breeders  to 
discontinue  their  selection  ?  How  can  we  do 
this  in  the  light  of  the  success  of  the  sugar 
beet  breeders?  Have  not  Sea  Island  cot- 
ton growers  increased  and  maintained  the 
length  and  fineness  of  their  staple  by  con- 
tinuous selection  ?  Have  not  corn  growers 
maintained  high  productiveness  of  different 
strains  by  selection?  Are  not  the  Jersey 
and  the  Holstein  maintained  at  a  high 
degree  of  efficiency  by  selection?  Has  not 
the  speed  of  our  trotting  and  pacing  horses 
been  increased  and  maintained  at  a  high 
rate  by  the  most  careful  selection  ?  To  one 
familiar  with  the  history  of  agriculture  and 
breeding  these  questions  arise  fast  and  are 


6 


SCIENCE 


likely  to  be  insistent.  There  can  be  no 
doubt  that  the  practical  breeders  have 
made  advances  by  selecting  from  the  best 
individuals.  No  genetist  or  scientific 
breeder  will  deny  this.  It  is  simply  the 
question  of  the  interpretation  of  how  the 
results  were  obtained  that  is  in  doubt  and 
whether  these  results  can  be  considered  as 
permanent,  new  unit  characters.  Before 
we  can  thoroughly  understand  this  subject 
it  is  probable  that  each  individual  case  will 
require  to  be  carefully  analyzed,  to  deter- 
mine the  nature  of  the  advance  made  and 
the  interpretation  of  the  process  or  proc- 
esses concerned.  At  present  we  can  only 
partially  understand  the  phenomena  pre- 
sented. 

It  appears  to  me  that  we  are  dealing 
in  breeding  with  two  markedly  distinct 
types  of  selection,  based  on  different  prin- 
ciples and  arriving  at  different  results, 
both  right  in  principle  and  productive  of 
equally  valuable  practical  results,  but  of 
very  different  value,  when  considered  from 
a  strictly  evolutionary  standpoint. 

It  would  seem  that  such  cases  of  im- 
provement as  are  illustrated  by  the  sugar 
beet  indicate  that  the  continuous  selection, 
generation  after  generation,  of  maximum 
fluctuations  shown  by  a  character,  will  re- 
sult in  maintaining  a  strain  at  nearly  the 
maximum  of  efficiency;  and  that  within  a 
pure  race  the  progeny  of  a  maximum 
variate  which  would  probably  be  classed  as 
a  fluctuation,  does  not  regress  entirely  to 
the  mean  of  the  race  in  the  first  genera- 
tion succeeding  the  selection,  but  that  we 
only  have  a  certain  percentage  of  regres- 
sion similar  to  the  regression  determined 
by  Galton.  It  would  further  seem  to  be 
indicated  by  the  evidence  now  avail- 
able that  in  some  cases  we  may  even  expect 
the  continuously  selected  strain  to  exceed 
the  ordinary  maximum  of  the  unselected 
population.  In  the  Illinois  corn  experi- 


ments the  maximum  oil  and  protein  con- 
tent seems  clearly  to  have  exceeded  the 
ordinary  maximum,  and  is  certainly  main- 
tained at  a  very  high  degree  with  a  new 
mode  and  range  of  variation.  If  a  new 
mutant  of  high  protein  content  has  been 
secured  in  the  course  of  the  experiments 
with  a  change  of  type  it  is  probable  that 
this  high  protein  content  will  behave  as  a 
unit  character  in  inheritance.  Upon  the 
other  hand,  if  the  results  are  interpreted  as 
simply  the  maintenance  by  isolation  of  a 
strain  produced  by  selecting  fluctuations, 
there  would  probably  be  a  rapid  return  to 
the  normal  range  of  variation  of  this  char- 
acter if  the  selection  was  discontinued. 

De  Vries  has  pointed  out  that  natural 
selection  can  produce  races  and  maintain 
them,  but  its  power  to  develop  races  be- 
yond the  natural  range  of  variability  re- 
mains to  be  demonstrated. 

With  reference  to  his  experiments  with 
the  potato  beetle  Tower  states: 

It  is  demonstrated  that  among  the  fluctuating 
variations  there  are  individuals  which  are  able  to 
transmit  their  particular  variation  and  give  rise  by 
selection  to  a  race,  while  the  majority  are  not  able 
to  hand  on  their  particular  conditions  to  their 
progeny.  Eaces  developed  by  selection  from  such 
variations  have  not  been  carried  beyond  the  normal 
limit  of  variability  of  the  species. 

These  races  or  selected  strains  maintain 
themselves  as  long  as  the  selection  is  con- 
tinued, and  when  the  selection  is  discon- 
tinued rapidly  regress  to  the  mean  of  the 
species. 

The  above  examples  from  the  sugar  beet, 
corn  and  potato  beetle  will  illustrate  the 
type  of  improvement  usually  secured  by 
practical  breeders.  By  their  selection  they 
maintain  a  strain  of  high  efficiency  without 
having  in  general  exceeded  the  limits  of 
variation  of  the  species  or  race  and  without 
having  produced  new  unit  characters  which 
would  be  maintained  without  selection  and 


SCIENCE 


segregate  as  pure  units  following  hybrid- 
ization. 

Our  different  breeds  of  dairy  animals  are 
maintained  in  a  state  of  high  productivity 
by  continuous  selection.  Cows  are  followed 
carefully  with  reference  to  their  milk-pro- 
ducing capacity  and  their  ability  to  trans- 
mit this  quality  to  their  offspring.  The 
ability  of  bulls  to  beget  high  milk-pro- 
ducing daughters  is  taken  as  a  test  of  their 
value.  There  can  be  no  doubt,  the  speaker 
believes,  that  this  selection  within  the 
breed  maintains  the  breed  in  a  state  of 
high  efficiency  and  is  absolutely  necessary 
to  the  success  of  dairying.  Strictly  speak- 
ing, in  the  course  of  this  selection,  however, 
no  new  type  has  been  produced.  It  is  well 
recognized  that  the  continuous  selection  is 
necessary  to  the  maintenance  of  high  milk- 
producing  capacity,  and  if  the  selection 
were  discontinued  the  average  milk  pro- 
duction of  any  dairy  herd  would  rapidly 
decline  until  it  reached  the  normal  mean 
for  the  breed  concerned.  The  same  can 
not  be  said,  however,  of  the  breed  or  race 
characters,  that  is,  those  characters  which 
distinguish  the  breeds  or  races  from  other 
breeds.  Selection  is  not  necessary  to  main- 
tain the  general  characters  of  the  Holstein 
breed  for,  as  long  as  it  is  not  crossed  with 
other  breeds,  it  will  in  general  maintain  its 
characters  so  far  as  color,  conformation,  and 
dairy  type  are  concerned.  The  same  may 
be  said  of  any  of  our  breeds  of  cattle  and 
horses.  The  high  efficiency  of  our  race 
horses  is  maintained  by  the  most  careful 
selection  and  yet  probably  in  most  cases  no 
distinctly  new  character  is  added,  which 
would  maintain  itself  as  a  unit  character  in 
inheritance. 

It  is  true  that  we  are  dealing  here  with 
complex  phenomena  and  limited  exact  ex- 
perimentation, and  a  distinct  mutant  in  the 
direction  of  high  efficiency  might  occur  at 
any  time  and  be  chosen  for  breeding  which 


would  maintain  itself  without  continuous 
selection. 

It  is  interesting  at  this  point  to  recall  one 
of  the  most  common  differences  between 
plant  and  animal  breeding  which  is  seldom 
clearly  recognized  by  practical  breeders. 
Plant  breeders  most  commonly  strive  to 
produce  new  races  or  breeds  with  dis- 
tinctive characters  which  will  reproduce 
their  desirable  qualities  without  continuous 
selection;  while  animal  breeders  almost 
wholly  limit  their  attention  to  selection 
within  the  breeds  already  established,  to 
maintain  them  in  the  highest  state  of  effi- 
ciency possible.  The  failure  to  understand 
this  difference  in  purpose  has  frequently 
led  to  confusion  in  our  discussions. 

It  is  beyond  the  scope  of  this  paper  to 
discuss  the  kinds  of  variation  used  in  these 
different  types  of  selection,  even  if  we  pos- 
sessed the  requisite  knowledge,  which  is 
doubtful.  The  speaker  may  be  pardoned, 
however,  for  digressing  far  enough  to  state 
that  it  is  his  conviction  that  there  is  no 
very  hard  and  fast  line  between  that  varia- 
tion which  is  in  considerable  degree  in- 
herited, such  as  is  found  frequently  in  high 
milk-producing  cows  in  selection  within  the 
breed,  and  the  mutation  which  gives  abso- 
lute inheritance  and  establishes  a  perma- 
nent new  mode.  The  great  difficulty  in 
determining  whether  there  is  any  true 
cumulative  action  of  selection  which  will 
extend  a  character  beyond  the  limits  of  the 
race  or  species  is  met  in  determining  what 
are  and  what  are  not  mutations.  My  ex- 
perience has  led  me  to  conclude  that  the 
continuous  selection  of  maximum  fluctua- 
tions in  a  certain  direction  may  in  some 
cases  lead  to  the  gradual  strengthening  of 
the  character  until  finally  it  may  become, 
more  or  less  suddenly,  fully  heritable  and 
it  would  then  be  recognized  as  a  mutation. 

In  many  cases  we  find  exceedingly  small 
differences  maintaining  themselves  genera- 


8 


SCIENCE 


tion  after  generation  under  different  en- 
vironments when  the  lines  of  descent  are 
kept  pure.  A  marked  illustration  of  this 
is  afforded  by  Mr.  Evans's  studies  on  pure 
lines  of  Stellaria  reported  at  this  meeting. 
The  segregation  of  such  characters  in  hy- 
bridization would  be  exceedingly  difficult 
to  recognize  if  it  did  occur.  Again  the 
occurrence  of  such  small  mutants,  if  we 
may  so  designate  them,  within  a  breed 
under  selection,  if  not  recognized  and  iso- 
lated, would  be  crossed  with  fluctuations 
and  cause  variations  which  would  be  recog- 
nized as  regressions  in  the  highly  selected 
strain. 

I  think  it  will  have  become  clear  from 
the  above  discussion  that  in  the  present 
state  of  our  knowledge  of  selection  we  can 
only  advocate  that  practical  breeders  con- 
tinue their  selections  as  in  the  past.  This 
is  particularly  true  in  the  cases  where  it 
is  the  idea  to  maintain  the  race  or  breed  at 
its  highest  efficiency.  In  the  case  of  plant 
breeders  working  to  produce  new  races,  the 
mutation  theory  introduces  a  new  element 
and  leads  the  breeder  to  search  for  a 
mutant  possessing  desirable  characters 
which  he  can  isolate  and  which  he  may 
expect  will  reproduce  its  characters  as  soon 
as  he  has  purified  the  type  from  mixtures 
derived  through  hybridization  with  other 
types.  He  will  select  the  type  to  purify  it 
rather  than  to  augment  its  good  qualities. 

Returning  again  to  the  question  of  new 
characters,  we  may  profitably  question 
more  definitely  where  such  new  characters 
come  from,  if  they  are  not  produced  by 
selection.  Clearly,  no  problem  is  of  more 
importance  to  the  breeder  than  to  be  able 
to  definitely  produce  or  cause  such  new 
characters  to  appear.  If  the  breeder  must 
await  the  pleasure  of  nature  to  secure  the 
changes  he  desires,  the  waiting  may  be  long 
and  tedious.  If  he  must  watch  thousands 
of  plants  of  a  certain  race  or  species  every 


year  in  order  to  find  the  apparently  acci- 
dental variation  or  mutation  in  the  direc- 
tion of  the  improvement  he  has  in  mind 
which  may  rarely  or  never  be  found,  the 
process  will  be  so  hazardous  that  we  should 
have  to  await  the  accidental  discovery  of 
any  new  characters.  Indeed,  up  to  the 
present  time  we  have  had  practically  no 
other  recourse  than  to  await  the  accidental 
discovery  of  such  new  characters.  We, 
however,  have  had  many  theorists  and  in- 
vestigators who  believed  that  changed  en- 
vironment would  stimulate  the  production 
of  variations  in  the  direction  of  better  fit- 
ting the  organism  to  its  environment. 
Lamarck  and  his  followers  have  strongly 
maintained  this  hypothesis  and  many  scien- 
tists even  to-day  believe  in  the  effectiveness 
of  environment  in  developing  adaptive 
changes.  Breeders  have  carried  this  prin- 
ciple so  far  as  frequently  to  advocate  the 
growing  of  plants  in  the  environment  most 
likely  to  produce  the  change  desired,  as,  for 
instance,  cultivating  tall  plants  like  twi- 
ning beans  in  the  north  or  at  high  altitudes 
if  it  is  desired  to  produce  a  dwarf  type  or, 
vice  versa,  breeding  the  plants  in  the  south 
and  at  a  low  altitude  if  a  giant  or  tall  type 
is  desired.  Weismann  and  his  school  of 
followers  have  apparently  exploded  this 
idea  by  demonstrating  that  characters  ac- 
quired as  a  result  of  changed  environment 
are  merely  physiological  changes  and  are 
not  inherited.  The  question,  however,  is 
by  no  means  settled  and  we  must  await  fur- 
ther evidence. 

Knight  believed  that  increased  food 
supply  caused  an  increase  in  the  range  of 
variation  and  that  it  was  important  for 
breeders  to  manure  their  plants  heavily. 
De  Vries,  on  the  contrary,  would  have  us 
believe  that  such  variations  are  fluctua- 
tions and  non-heritable.  The  studies  of 
Weisse,  Reinhold,  MacLeod,  Tammes  and 
Love  have  given  us  many  instances  where 


SCIENCE 


the  range  of  variation  is  increased  as  a  re- 
sult of  food  supply  and  other  instances 
where  the  variation  is  apparently  greater 
on  poor  or  sterile  soil. 

It  would  seem  that  any  treatment  that 
would  increase  the  range  of  variation,  in 
plants  that  are  grown  for  breeding  pur- 
poses would  be  valuable,  but  it  still  remains 
to  be  definitely  proved  whether  such  in- 
creases in  the  range  of  variation  are  in  any 
marked  degree  heritable  and  whether  valu- 
able maximum  variates  can  be  more  fre- 
quently produced  in  this  way  than  would 
be  found  in  similar  groups  of  plants  under 
ordinary  treatment. 

It  is  only  very  recently  that  the  idea  has 
developed  that  we  can  go  farther  than  pos- 
sibly change  the  environment.  With  the 
publication  of  MacDougal's  researches  in 
1906  describing  mutations  that  were  ap- 
parently caused  by  injecting  the  capsules 
of  plants  with  certain  solutions,  such  as 
zinc  sulphate,  magnesium  chloride  and  the 
like,  a  possible  new  method  of  forcing 
variations  was  introduced.  MacDougal 
apparently  obtained  marked  variations  as 
a  result  of  his  treatment,  which  were  in- 
herited in  succeeding  generations. 

Tower,  by  subjecting  potato  beetles  dur- 
ing the  formation  of  the  germ  cells  to  ex- 
tremely hot  and  dry  or  hot  and  humid 
conditions  with  changes  of  atmospheric 
pressure,  was  able  to  cause  the  development 
of  marked  changes  or  mutations  which 
were  found  to  transmit  their  characters 
true  through  several  generations  and 
which  segregated  as  unit  characters  follow- 
ing hybridization.  He  concludes  from  his 
experiments  ' '  that  heritable  variations  are 
produced  as  the  direct  response  to  external 
stimuli." 

Gager  has  produced  similar  changes  in 
plants  by  subjecting  the  developing  ova- 
ries of  plants  to  the  action  of  radium  rays 
and  a  number  of  similar  studies  by  Hert- 


wig  and  others  indicate  that  radium  ema- 
nations have  a  very  active  effect  on  both 
plants  and  animals. 

While  the  evidence  favoring  the  value  of 
such  external  stimuli  as  the  above  in  pro- 
ducing new  heritable  characters  is  appar- 
ently definite  and  positive,  the  extent  to 
which  the  method  can  be  used  in  practical 
breeding  has  not  been  determined,  and  in- 
deed we  must  await  further  evidence  be- 
fore we  can  finally  accept  the  evidence,  or 
the  interpretation  of  the  evidence,  pre- 
sented in  these  very  valuable  and  suggest- 
ive researches.  Dr.  Humbert  carried  out 
experiments  in  the  speaker's  laboratory  in 
which  the  capsules  of  a  pure  line  of  a  wild 
plant  Silene  nocti flora  were  injected  with 
the  solutions  used  by  Dr.  MacDougal,  and 
although  the  number  of  plants  handled 
(about  15,000)  was  apparently  as  great  or 
greater  than  was  used  in  MacDougal's 
experiments,  no  mutations  were  found  in 
the  treated  plants  which  were  not  also 
found  in  the  untreated  or  check  plants. 

Some  observations  and  experiments  are 
recorded  in  literature  which  indicate  that 
mutilations  or  severe  injury  may  induce 
the  development-  of  mutations.  Most  note- 
worthy among  such  observations  are  those 
of  Blaringham,  who  by  mutilating  corn 
plants  in  various  ways,  such  as  splitting 
or  twisting  the  stalks,  apparently  produced 
variations  which  bred  true  without  regres- 
sion and  which  he  described  as  mutations. 
My  own  observations  on  the  great  fre- 
quency of  striking  bud  variations  on  re- 
covering trunks  of  old  citrus  trees  in 
Florida,  following  the  severe  freeze  of 
1894-5,  also  furnished  evidence  in  sup- 
port of  this  theory. 

In  general,  it  is  assumed  that  in  hybridi- 
zation we  are  dealing  merely  with  charac- 
ters already  present  and  that  new  charac- 
ters which  appear  are  due  to  the  different 
reactions  caused  by  new  associations  of  unit 


10 


SCIENCE 


characters  in  their  mutual  effect  on  one 
another.  It  is,  however,  possible  that  new 
unit  characters  may  result  from  the  com- 
mingling of  the  different  hereditary  units 
which  are  to  be  considered  as  mutations 
rather  than  new  combinations.  As  is  well 
known,  Weismann  long  ago  advanced  the 
hypothesis  that  valuable  variations  in  evo- 
lution were  due  to  the  commingling  of 
protoplasms  from  different  parents  having 
different  hereditary  tendencies,  a  process 
which  he  called  "  amphimixis."  He  did 
not  have  in  view,  however,  the  formation 
of  new  unit  characters  as  distinct  from  new 
combinations. 

The  most  marked  case  known  to  the 
speaker,  of  the  appearance  of  a  new  char- 
acter which  was  apparently  caused  by  the 
stimulation  of  hybridization,  is  the  devel- 
opment of  a  marked  spur  or  horn  on  the 
lip  of  a  hybrid  Calceolaria.  This  occurred 
among  a  series  of  hybrids  between  a  her- 
baceous and  a  shrubby  species  made  by 
Professor  Atkinson  and  Mr.  Shore,  of  the 
botanical  department  at  Cornell  University. 
One  or  two  tapering  horns  about  an  inch  in 
length  and  from  2  to  4  millimeters  in  diam- 
eter at  the  base,  spring  from  the  upper  sur- 
face of  the  large  corolla  lip  and  grow  erect 
to  its  surface.  No  such  character,  so  far  as 
can  be  learned,  is  known  in  the  Calceolarias 
and  it  would  seem  to  have  been  caused  by 
the  hybridization.  It  can  not,  apparently, 
be  considered  as  a  combination  of  any  of 
the  known  characters  of  the  species  con- 
cerned. 

Such  apparently  new  characters  appear 
rather  commonly  among  large  batches  of 
hybrids,  and  while  there  is  little  evidence 
available  on  the  subject,  I  am  inclined  to 
believe  it  will  be  found  that  hybridization 
may  stimulate  the  production  of  new  unit 
characters,  which  mendelize  with  the  pa- 
rental types. 

While  the  evidence  at  our  command  re- 


garding the  artificial  production  of  muta- 
tions is  not  yet  sufficiently  exact  and  trust- 
worthy to  enable  us  to  draw  definite  con- 
clusions and  formulate  recommendations 
for  practical  breeders,  it  may  be  stated 
that  this  is  apparently  one  of  the  most 
profitable  lines  of  experimentation  for  the 
immediate  future. 

Thus  far  I  have  only  incidentally  dis- 
cussed hybridization  and  the  advance  of 
our  knowledge  in  this  direction.  The  scope 
of  this  address  will  not  allow  of  an  ade- 
quate treatment  of  this  subject  and  it  ap- 
peared wiser  to  discuss  more  in  detail  the 
problems  of  selection  and  variation.  I 
can  not,  however,  close  this  address  with- 
out referring  to  this  very  important  field 
of  genetics. 

No  discovery  in  the  field  of  breeding  has 
had  more  effect  or  is  more  far  reaching  in 
its  importance  than  the  discovery  of  what 
have  now  come  to  be  known  as  Mendel 's  prin- 
ciples of  heredity.  While,  as  stated  in  the 
beginning  of  this  address,  breeders  had  long 
before  the  rediscovery  of  Mendel's  papers 
come  to  understand  that  there  was  a  segre- 
gation of  characters  in  the  F2  generation 
and  that  it  was  possible  to  recombine  in 
certain  hybrids  the  desired  characters 
from  different  parents,  there  was  no  defi- 
nite understanding  of  the  underlying 
principles,  and  no  conception  of  the  almost 
infinite  possibilities  of  improvement  which 
the  field  of  hybridization  opened  to  us. 

The  law  of  dominance,  while  not  univer- 
sal, has  explained  many  cases  of  prepo- 
tency in  one  generation  and  failure  of  cer- 
tain individuals  to  transmit  the  character 
in  the  next  generation.  It  has  explained 
many  cases  of  latency  of  characters  and 
may  account  for  all  such  cases. 

The  law  of  segregation  has  shown  us 
that  the  splitting  of  characters  follows  a 
definite  method  and  that  we  can  in  general 
estimate  the  frequency  of  occurrence  of  a 


SCIENCE 


11 


certain  desired  combination,  if  we  know 
the  characters  concerned  to  be  simple  unit 
characters. 

The  study  of  hybrids  has  been  resolved 
into  a  study  of  unit  characters  and  their 
relation  to  each  other.  By  hybridizing  re- 
lated types  having  opposed  characters  and 
observing  the  segregations  which  occur  in 
the  later  generations,  we  analyze  the  char- 
acters of  each  type  and  determine  when  we 
have  a  character  pair.  The  researches  on 
this  subject  by  Mendel,  Bateson,  Daven- 
port, Castle,  Punnett,  Shull,  Hurst,  Cor- 
rens,  Tschermak,  East  and  dozens  of  other 
now  well-known  investigations,  have  de- 
veloped a  science  of  heredity  of  which  we 
had  no  conception  a  few  years  ago. 

We  can  now  study  the  characters  pre- 
sented by  the  different  varieties  of  a  plant 
or  of  different  species,  which  can  be  crossed 
with  it  and  definitely  plan  the  combination 
of  characters  desired  in  an  ideal  type,  and 
can  with  considerable  confidence  estimate 
the  number  of  plants  it  will  be  necessary 
to  grow  to  get  this  combination.  We  now 
know  in  general  how  characters  behave  in 
segregation  and  inheritance  so  that  we  can 
go  about  the  fixation  of  a  desired  type, 
when  one  is  secured,  in  an  orderly  and  in- 
telligent way. 

The  farther  the  study  of  characters  is 
carried  the  more  we  are  coming  to  realize 
that  the  appearance  of  apparently  new 
types  following  hybridization  is  due  to  re- 
combinations of  different  units  which  in 
their  reactions  give  apparently  new  char- 
acters. As  an  illustration,  in  a  study  of 
pepper  hybrids  which  I  have  carried  on 
during  the  past  four  years  it  has  become 
evident  that  the  form  of  plant  and  branch- 
ing is  due  to  three  pairs  of  characters  or 
allelomorphs;  namely,  first,  erect  or  hori- 
zontal branches;  second,  large  or  small 
branches ;  and  third,  many  or  few  branches. 
In  crossing  two  medium-sized  races,  one 


with  large,  horizontal  and  few  branches, 
and  the  other  with  small,  erect  and  nu- 
merous branches,  there  result  many  new 
combinations  of  characters,  among  which 
appear  some  with  small,  horizontal  and  few 
branches,  which  gives  a  dwarf  plant,  and 
others  will  have  a  combination  of  large, 
erect  and  numerous  branches,  which  gives  a 
giant  plant.  These  dwarfs  on  the  one  hand 
and  giants  on  the  other,  appear  as  distinct, 
new  creations,  though  they  are  very  evi- 
dently merely  the  recombinations  of  al- 
ready existing  unit  characters,  and  dwarf- 
ness  and  giantness  are  the  results  of  the 
reaction  of  the  different  units  combined. 

When  we  remember  the  large  number  of 
distinct  characters  which  are  presented  by 
the  very  numerous  varieties  of  any  of  our 
cultivated  plants,  we  arrive  at  an  under- 
standing of  the  possibilities  of  improve- 
ment which  the  field  of  hybridization  af- 
fords, yet  I  doubt  if  many  of  us  have  even 
then  an  adequate  conception  of  the  possi- 
bilities. Possibly  I  may  make  this  more 
clear  by  an  illustration  from  my  timothy 
breeding  experiments.  While  the  various 
characters  presented  by  the  different  types 
under  observation  have  not  been  carefully 
studied  in  inheritance,  the  following  char- 
acters can  be  distinguished  plainly,  and 
from  observations  on  accidental  hybrids  are 
known  to  segregate.  The  following  is  a  list 
of  28  such  character  pairs  which  it  is  be- 
lieved will  prove  to  be  allelomorphs. 

TIMOTHY    CHABACTEE   PAIBS 

Heads 

Long  or  short. 

Thick  or  thin. 

Dense  or  lax. 

G^nish  or  purple  when  young. 

Gray  or  tawny  when  ripe. 

Simple  or  branched. 

Erect  or  nodding. 

Continuous  or  interrupted. 

Apex  blunt  or  pointed. 

Base  blunt  or  attenuated. 

Seeds  large  or  small. 


IV/6 


12 


SCIENCE 


Leaves 

Long  or  short. 

Broad  or  narrow. 

Erect  or  reversed. 

Boiled  or  flat. 

Clustered  at  base  or  extending  to  top  of 

culm. 
Culms 

Tall  or  short. 

Thick  or  thin. 

Straight  or  wavy. 

Erect  or  bent  outward. 

Green  or  purplish. 

Many  or  few. 
Nodes 

Many  or  few. 

Green  or  brown. 

Internodes  long  or  short. 
Habit  Characters 

Lodging  or  non-lodging. 

Eusty  or  rust  resistant. 

Early  or  late  season. 

It  is  possible  that  some  of  these  char- 
acters may  be  expressions  of  the  same  unit, 
but  in  a  number  of  cases  they  certainly  re- 
present several  different  unit  characters. 
For  instance  in  length  of  head,  height  of 
culm,  number  of  culms,  and  season  of  matur- 
ing, several  different  degrees  are  certainly 
present  which  are  fully  heritable.  Doubt- 
less there  are  many  more  than  28  pairs  of 
unit  characters  which  could  be  distin- 
guished by  careful  study.  If  we  have  two 
pairs  of  characters,  such  as  tall  or  short  and 
early  or  late,  we  know  that  4  homozygous 
combinations  are  possible.  If  three  pairs 
are  considered,  8  combinations  are  possible. 
Every  time  we  add  a  different  character 
pair  we  double  the  number  of  different 
combinations  that  are  possible.  Twenty- 
eight  character  pairs  would  thus  give 
us  as  many  possible  combinations  as  2 
raised  to  the  28th  power,  or  the  astonish- 
ing number  of  268,435,456.  It  would  be 
possible  then  to  produce  this  tremendous 


number  of  different  varieties  of  timothy  if 
there  was  any  reason  to  do  so,  and  each  va- 
riety would  be  distinguished  from  any 
other  variety  by  one  distinct  character  and 
would  reproduce  true  to  seed. 

The  task  of  the  breeder,  then,  is  to  find 
which  among  these  character  combinations 
gives  the  superior  plant  for  commercial 
cultivation.  He  will  soon  eliminate  cer- 
tain characters  as  unimportant  and  con- 
centrate his  attention  on  those  qualities 
that  are  essential. 

It  would  be  interesting  to  discuss  the 
factor  hypothesis,  purity  of  germ  cell,  sex- 
limited  inheritance  and  other  important 
problems  connected  with  inheritance  stud- 
ies, but  I  have  already  too  severely  tested 
your  endurance. 

As  breeders  and  genetists  we  have  every 
reason  to  congratulate  ourselves  on  the 
rapid  advance  of  our  science  and  the  grow- 
ing recognition  of  the  importance  of  the 
subject  in  practical  agriculture.  Colleges 
throughout  the  country  are  extending  their 
courses  of  study  to  include  genetics.  In 
almost  all  of  the  experiment  stations  stud- 
ies on  genetics  and  practical  breeding  are 
now  given  fully  as  much  attention  as  any 
other  subject.  With  all  of  this  advance, 
however,  only  in  a  few  institutions  have 
there  been  established  special  professor- 
ships or  investigatorships  in  breeding 
or  genetics.  If  the  subject  of  genetics  is  to 
be  properly  taught  or  the  investigations 
are  to  reach  the  highest  standard,  it  is  clear 
that  men  should  have  this  as  their  special 
and  recognized  field.  The  subject  should 
no  longer  be  assigned  indiscriminately  to 
the  horticulturist,  agronomist,  animal  hus- 
bandmen or  dairymen.  We  must  establish 
more  professorships  of  genetics  or  breeding. 
HERBERT  J.  WEBBER 

COBNELL  UNIVERSITY 


UNIVERSITY  OF  CALIFORNIA  AT  LOS  ANGELES 

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